Engine and Transmission Tech

Hi all
i cant believe ive just discovered this site and forum.

Hopefully you guys can offer me some good advice.

I have a TVR Chimaera 450 which i drag race as well as use for pleasure and i drive to the dragstrips.
Over the last 18 months i have experimented with nitrous oxide and have cut my 1/4 mile times to 11.6 with a best terminal of 125.

I am stripping the 105k engine for a full rebuild and i intend to fit forged pistons along with ARP bolts etc. The heads are big valve 43/37mm and will be home ported and fitted with new shortened guides.

I still wish the car to be fairly road friendly but am willing to sacrifice a little in order to get benefits when injecting around 300bhp of nitrous.

I am looking for any advice and suggestions, particularly on cam choice.
Hope you can help,
Derek

I wish I could give you cam advice. I haven't run my engine yet though. I was advised by Dan Jones and Woody at the Wedge Shop that these engines like a tighter LCA. My cam is at about 108º. Well here's my cam specs, anyway. My engine is a stroker so it displaces more at ≈ 5 liters. But just in case it's useful. I expect Dan and a couple other guys will chime in soon. Keep in mind that you need more compression as the overlap goes up. I make 12.5:1 CR but my DCR is 9.54:1.

LCA: 108º
Overlap: 74º
Timing: 35/71/75/39

Clearance Hot: 0.023

Lift: .544/.544

Adv Duration: 286/294


Specs @ 0.050:

Overlap: 38
Timing: 17/53/21/57

Duration: 250/253


Now there are a couple factors that make my engine different. I'm using Chevy Z28 rods that are 5.7" and the Buick 3.4" crank so my rod ratio is at 1.68:1. Your rod ratio is more like 1.82:1 so that changes things a bit...

Hello Derek,

If you'll be running nitros, definitely make sure you install those forged pistons. The Hypereutectic pistons ie: cast will not stand up to the increased stresses. Forged steel rods are also suggested as a reliable, strong option.

Also, steel head gaskets will help contain the increased compression pressure.

Check heads for straightness.

Since you'll be completely rebuilding the motor, I suggest looking into top hat liners and have the block checked for porosity and cracking behind the liners... as this is a major issue with these motors.

Forged crank over a cast unit.

Nicholas and others here really know what they're talking about so look to them for sound advice, too.

Trip